From: moroney@world.std.spaamtrap.com   
      
   hancock4@bbs.cpcn.com writes:   
      
   >Regarding Amtrak's ex-PRR NEC, would anyone have any idea of the dollar   
   >amount needed up front to convert it from 25 Hz to 60 Hz, and then the   
   >savings and payback time?  Would a frequency change impact the signal   
   >system, any rolling stock, or auxiliary equipment?   
      
   Apparently signalling uses its own oddball frequencies.  I've seen 100 Hz,   
   91 2/3 Hz and 250 Hz mentioned, with 91 2/3 Hz used in 25 Hz power regions   
   rather than 100 Hz because the signal system can't be a harmonic of the   
   power system.   
      
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